Genuine New VT VU VX VY VZ WH HSV GTS GTO and Holden Commodore Monaro Headlight, Headlamp, Head Light H1 Globe Bulb Dust Cap Cover and O-Ring.

This is the smaller cover on the outer side and the diameter is 7.5cm.  

Part Number on the cover is 11063919 which is the replacement globe number. The actual cap part number is 92140531